The present invention is directed to a method for detecting and combatting enemy helicopters by means of a missile that has an infrared homing head with an infrared lens and an infrared sensor that will emit electrical signals, depending on the incident of infrared radiation, which sensor is designed as a two-dimensional detector matrix consisting of a number of punctiform detector cells arranged essentially in the focal plane of the infrared lens. To determine the target information of a detected helicopter, the punctiform detector cells are individually scanned quickly one after another by an evaluation device to determine the amplitude and the frequency of the electrical signals, so that nearly a simultaneous transmission of all measured values will take place so that the homing head flying over the helicopter will pick up the infrared radiation released upward by the helicopter's propulsion turbine and exhaust gas plume and modulated by the helicopter rotor blades to determine the helicopter's relative position on the optical axis of the homing head, and after completion of the target recognition carried out by a time series analysis of the modulated infrared radiation of the helicopter, steers a missile equipped with an active charge until it hits the target.
A method is known from U.S. Pat. No. 5,400,134, whose disclosure is incorporated herein by reference thereto and which claims priority from German Patent Application 37 33 681. This method uses a missile which has a matrix detector, which is firmly connected with the missile, and the optical axis of the matrix extends parallel to the missile's longitudinal axis. A large field of view required to combat targets operating in a concealed manner, which can only be reconnoitered with corresponding inaccuracy, is achieved by use of a wide-angle lens with relatively low resolution. The infrared radiation typical of the target, which radiation is modulated by the operation of the helicopter's rotors, is used as a characteristic feature for target-type recognition.
This known method has thoroughly proven itself. However, the procedure comes up against certain limits, particularly when the speed of the missile serving as a homing head carrier and, thus, also of the matrix detector, exceeds certain values. In this case, if the modulation amplitude of the target, for example the helicopter to be detected, is also small, as is the case, for example, when camouflaging measures are provided on the helicopter, and if the contrast range of the background is also high, the target recognition and target-type recognition are much less likely to be achieved.
On the other hand, it is already known to use an infrared-sensitive homing head for which a matrix detector operated with high resolution is swung by means of a gimbal and in this way, in connection with level motion of the missile, scans the field of view for the targets. With this method, target acquisition and target-type recognition are carried out with methods of image processing, for example, individual images are examined on the basis of overall contrast range, distribution of the contrast and gradients, among other things. This method, in turn, has its limits when the line of sight between the missile and the helicopter to be detected becomes too long and/or different helicopters display similar geometric features. In this case, the image-processing homing head is indeed still able to recognize helicopters as such, but the likelihood of successful target-type recognition is clearly reduced.
It is already known from German Patent Application 33 26 233 to make a distinction by means of a target homing head, between a target-seeking phase, in which the entire field of view is scanned, and an approach phase, in which only the immediate surroundings of the target point are scanned, and to switch the scanning motion accordingly. In so doing, it is necessary to execute the target-type recognition already in the target-seeking phase.